Safety control for hydraulic brake systems



June 25, 1946. c. w. HAGGART SAFETY CONTROL FOR HYDRAULIC BRAKE SYSTEMS Filed Dec. 20, 1943 :Fi'- 5- lnr enlolt as 2 Patented June 25, 1946 SAFETY CONTROL FOR HYDRAULIC BRAKE SYSTEMS Crichton W. Haggart, Toronto, Ontario, Canada, assignor of one-third to John C. Urquhart,

Toronto, Ontario, Canada Application December 20, 1943, Serial No. 515,048

v Claims.

- r 1 The present invention is particularly adapted to the braking systems of automotive vehicles, though it may be applied to other hydraulic systems where conditions similar to those found in occurs in any branch of the system the faulty branch will be automatically isolated, thereby enabling the remalningportions of the system to operate normally V L ,l

, A' further object ofthe present invention is: to provide a system which will allow slight operational fluid. loss, in difleren tfbranches without impairingthe system as a whole, and further, to provide a safety devicegin whichall the parts will have the same co-emcient of expansion.

A further object is to provide a safety device which will allow the complete andeasy removal of all air in -thesystem and'in. which there'will not be sufiflcient, friction in the operating parts to disturb the proper equalizing of the pressure.

A still further object is to provide a system which can be bledland thedevice placed in operationin .the minimum of time.

The principal features of the invention consist in the novel arrangement of individual cylinders in each branch of a hydraulic system, which cylinders are connected through a common duct to the operating or master cylinder, and individual pistons are arranged within each of said cylinders which will, through excessive leakage in any branch, automatically close the same to retain the fluid in the master cylinder and other branches from loss and operative impairment.

A further important feature consists in the novel provision of meanswherebyexcess fluid,

duetoexpansion, will be-by-passed back to the master cylinder and reservoir.

' A still further and important feature consists in'the novel arrangement of passages through the valving pistons with check valvesto compensate for fluid losses or contraction in the branches of the system. v

"A still further important feature consists in the novel provision of a control valve in the conduit connecting the master cylinder with the piston valve containing branch cylinders to enable the system to be bled to remove air therefrom.

In the accompanying drawing Figure 1 is a diagrammatic plan view of the chassis of a motor vehicle showing the application of my invention thereto. 1

Figure 2 is an enlarged plan view of the safety unit made in accordance with thi invention.

Figure 3 is a horizontal plan section through the unit taken on the line 33 of Figure 4.

Figure 4 is a vertical transverse sectional view taken on the line 4--4 of Figure 2.

Figure 5 is a vertical section taken on the line 5-5 of Figure 4.

In the installation of an, equipment embodying the present invention in a motor vehicle, as illustrated in the accompanying drawing, a master cylinder l, suitably mounted in the frame of the vehicle and having an operating pedal 2, is connected by a conduit 3 with a valve chamber 4 formed in a block 5.

Within the block 5 and at one side of the entrance thereto of the conduit 3 is a valve seat 6 leading to a passage 1 which communicates with an escape duct 8 leading out through the top of the block 5 and which is closed by a, threaded sealing plug 9. v

A valve In arranged within the valve chamber 4 has a bevelled surface to engage the seat 6, the stem of the valve extending through the passage and being threaded in a threaded orifice in the block.

The outer end of the valvestem II is sealed with a packing nut H. The inner end of the valve I0 is provided with a bevelled surface l3.

which is adapted to engage a bevelled seat l4 arranged in a plug l5 screwed into the block 5 and which encloses the valve chamber 4.

A lateral passage iii in the plug l5 leads radially outward through the block 5 and communicates through a ferrule I! with a passage l8 arranged in a block l9 which forms part of or is secured to the block 5.

A duct 20 leads from the recess in the plug l5 outside of the valve chamber 4 and this is closed with a screw plug 2|.

The passage 18 extending downwardly from the valve chamber communicates with a transverse passage 22 in the lower block l9 which is closed at the outer end by a screw plug 23.

,A pair of lateral passages 24 connected with the passage 22 open into threaded recesses 25 arranged in opposite sides of the block l9. Secured in each of the threaded recesses 25 is a cylinder 25, each of which communicates with the transverse passage 24 connected with the of'the ducts andports. c v

branch a i then.- ccnnected valve chamber 4, and the outer end of each cylinder is closed with a tubular plug 21, each of which has a pipe connection nipple 28 to which the branch pipes 29 of the braking system are connected.

Within. each of. the cylinders 26. is arranged a piston 30 which is adapted to be moved with the flow of fluid pressure applied from the master cylinder I, flowing through the conduit 3,

valve chamber 4 and passages I8, 22 and 24.

Each of said pistons is formed with an axial recess 3| housing a spring-held ball check valve 32 which engages the opening. in. a ferrule 33 in the inward pressure end. Asmall. bleed. opening 34 extends from the other end of the recess: 3| and communicates with the. interior of the.

against admission of. pressurefluid thereto from.

the'duct [Bjby a spring. ball check 31'. V

The 'entire unit described is preferably mounted in a plate. retainer 38, a particularl shown in Figure 2. This .unit. isirigidly mounted on the frame of the vehicle atja. level position. and connected with the master cylinder. Fluid. is then. pumped into theunit. by means of the. operating pedal. andthe pistons 3flareheld in position by the. use of..a suitable. rod until. fluid; runsfreely out. of the outer. endof the cylinder. This,.re-, moves..-air from inside. the pist'onland from...ahy.

' Each wheel cylinder to the outer nipple ends of theindiyidual. cylinders. The. valve J ll is then; turned. clockwise. until its: inner end. isfirmly seated; against the. seat |.4..

1 A short length. offpipe' 39., indicated by dotted: lines in Figure 2, is connected between-the. duct 8 in theblock. 4 anda port. Ailat. the. outer. end of one. of. the cylinders, and While-the. connection. of. the. conduit. 3; leading to. the Wheel cylinder. is: connected-to. the. wheelcylinder and the wheel. cylinder is adjusted to be allowed to ble.ed, fluid: is pumped into thev port 40-tQflll the outer end of the. cylinder 25. and the conduit. 3. and the wheelcylinder to. excludeall air, Thewheel cyl inder is then. sealed. and the branch thus treated willbe completely filled with. fluid exclusive of. air.

This. process is. repeated with each branch of thesystem until it is allcompletely filled. The auxiliary pipe 3,!) isthen removed and the duct 8 is sealed by'returning the screw plug 9', andeach of the ducts 40 is sealed with a suitable plug.

Upon'the completion of the filling of the system with fluid the valve I6 is then turned anti-clockwise to open the Valve chamber 4' to communicate with the passages l5 and I8, and the valve. is brought into engagement with the outer seat 6 of the valve chamber, thus completely sealing the oil chamber.

' The system. when thus filled will of course be properly tested for leaks, and providing the system is properly sealed it is then ready for operation. In the event of air entering the system through the master cylinder it will b necessary 4 to bleed the entire system and fill with fluid to ensur that there will be no entrapped air.

It will be remembered that in the setting of the system the pistons 30 are located midway of the length of each of the cylinders 26, and in the operationof the brake pedal. and master cylinder, pressure applied; to the fluid causes the pistons 30 to oscillate back and forth within the cylinders. The outward movement of the pistons forces fluid from the outer ends of th cylinders to the wheel cylinders, thereby operating the brakes.

It. will. be: understood that in normal operation the. slidingpiston-valves will not be forced to the ends ofthe cylinders as the wheel brakes will be fully applied when the pistons are in an intermediate position. If; however, there should be loss of: fluid in any one branch of the system the piston in that branch will, upon application of pressure through. the master cylindentravel. to the. end of the cylinder; and close the passage. This actionv is instantaneous and the-pressure on the fluid will. operatively affect the remaining;

. normally operating branches, while the one in inward end, it will open the port allowing-the which a leak has taken place will be out offi If excess expansion takes place in the. fluidin any one. branch the: piston valve. will move inwardly towardthe block [9 and, on reaching the excess fluid to flow into the port" 35 and" back to the passage l8 past the ballvalve 31; thereby returning to the master cylinder. 7

Compensation for fluid lossesand flui'd'contractions between, and including; the sliding piston. I

return through thepiston', consequently the. in-

crease in volume of "thereturning fluidforces' the piston. all the way back. to the central blocker distributor body and the excess fluid escapes through the expansion port which is uncovered by the; piston...

A device as herein described; has been thoroughly tested and foundto; operate satisfactorily with-a pressure Qr ZOOO'lbs; per squareinch' and.

higher pressures may be usecl'iifv found desirable. The unit may be constructed; entirely of. the

same metal so that. it will have a unitary co-efll-.

cient 01f expansion; All the parts are of" metal and they will not be aiiect'ed by the fluid and there will be no cause of failure because ofthe use ofmaterialsother than metal.

The design 'ofunit herein illustrated and described enables the easy and simple removal of all air from the entire systemg and it'willbeanoted that. in bleeding the; unit; theflow is: continuously upward. making: it impossible. to trap; ail:

part thereof.

The. form ofg valve; 30 for. sealing the sys em renders it leak-proof under operating conditicns The. device. issimple. an the number of: operating partsisreduced tothe-minimum, andthere are no parts to. wear toany, material extent. and

whatever wear may occur through. long andcon stant use will not afiect in any manner the sein any;

curity and accuracy of the device. Any addi tional clearance of the sliding piston valves will not harm the operation but will add to the compensating eifect from fluid losses.

The construction of the unit as herein described will permit any part thereof to be serviced or removed without disturbing the remaining construction.

What I claim as my invention is:

1. In a safety device for branched hydraulic systems, the combination with a plurality of branches and a master cylinder, of a block having a conduit connected with the master cylinder, said conduit having a plurality of branches, cylinders mounted in said block and having their inner ends communicating with the branchesof said mean conduit and their outer ends communicatin each with one of said system branches, pistons operating in said cylinders and adapted on engaging the ends of the cylinders to close the flow of fluid thereto from the master cylinder, a valve block mounted on the aforesaid block formed with a valve chamber having a conduit connected with the branched conduit in the aforesaid block, said valve chamber having seats at opposite sides thereof, a double seated valve adapted to be operated to selectively close the aforesaid seats, a port leading from the master cylinder to said valve chamber between said seats, and auxiliary ports in said valve chamber block arranged outwardly from said seats and adapted to communicate alternately with the valve chamber upon the operation of the valve.

2. A safety device for branched hydraulic systems, comprising the combination with a master cylinder and branch pressure services, of a block having a conduit connected with the master cylinder, said block having a plurality of branch openings leading from said conduit, a plurality of cylinders rigidly mounted in said block and each having its inner end' communicating with the master cylinder through one of said branch openings, the outer ends of said cylinders being each connected with one of the service branches, pistons operative one in each of said cylinders and adapted to close off the service branch connected with said cylinder 0n the excessive reduction of pressure therein, ports arranged adjacent to the inward ends of each of said cylinders communicating with a common return conduit connected with the aforesaid block conduit, a check valve permitting outflow of fluid pressure from said return conduit to the block conduit and preventing entrance of pressure from the first-mentioned conduit, and means connected with said block for controlling the flow of pressure fluid to the first-mentioned conduit therein and to the cylinders connected therewith.

3. In a control device of the class described, in combination, a main body having a fluid supply passage, a common pressure relief passage paralleling said supply passage, a plurality of cylinders radiating from said passages each communicating with the fluid supply passage at the inner end and each having a port opening therefrom intermediate of the length, all of said ports being connected to said common relief passage, means forming a non-return connection from said common pressure relief passage to said fluid supply passage, and pistons in said cylinders cooperating with said ports, said cylinders being adapted for connection to service branches.

4. A control device as claimed in claim 3 in which said block is provided with oppositely paired shallow threaded bores presenting bottom seating faces, the cylinders being threaded into said bores and sealingly engaging said faces at the inner end, said fluid supply passage having oppositely paired ports opening into the respective paired cylinders, oppositely paired ports opening from said pressure relief passage through said seating faces, said cylinder ports having passages leading through the walls of said cylinders and registering with said last-mentioned paired ports.

5. In a safety device for hydraulic pressure systems, the combination with a master cylinder and branch hydraulic leads, a plurality of cylinders one connected with each branch, means forming a common connection between said master cylinder and the cylinders connected to said branches, of pistons mounted one in each of said branch cylinders adapted to individually close the branch leadin from the cylinder upon the abnormal reduction of pressure Within said branch, said pistons each being formed with an orifice leading from the master cylinder connection and terminating in a bleed orifice the outer end of which is offset from alignment with the branch lead from the cylinder and sealed by contact with the end of the cylinder, and a check valve arranged in the piston orifice adapted to close the entrance of said orifice against the backflow of pressure through the bleed orifice.

CRICHTON W. HAGGART. 

